To meet the demand for wireless data traffic having increased since deployment of 4G (4th-Generation) communication systems, efforts have been made to develop an improved 5G (5th-Generation) or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘beyond 4G network’ or a ‘post LTE system’.
The 5G communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higher data rates. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), full dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed in 5G communication systems.
In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud radio access networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, coordinated multi-points (CoMP), reception-end interference cancellation and the like.
In the 5G system, hybrid FSK and QAM modulation (FQAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed.
The Internet, which is a human centered connectivity network where humans generate and consume information, is now evolving to the Internet of Things (IoT) where distributed entities, such as things, exchange and process information without human intervention. The Internet of Everything (IoE), which is a combination of the IoT technology and the Big Data processing technology through connection with a cloud server, has emerged. As technology elements, such as “sensing technology”, “wired/wireless communication and network infrastructure”, “service interface technology”, and “Security technology” have been demanded for IoT implementation, a sensor network, a Machine-to-Machine (M2M) communication, Machine Type Communication (MTC), and so forth have been recently researched. Such an IoT environment may provide intelligent Internet technology services that create a new value to human life by collecting and analyzing data generated among connected things. IoT may be applied to a variety of fields including smart home, smart building, smart city, smart car or connected cars, smart grid, health care, smart appliances and advanced medical services through convergence and combination between existing Information Technology (IT) and various industrial applications.
In line with this, various attempts have been made to apply 5G communication systems to IoT networks. For example, technologies such as a sensor network, Machine Type Communication (MTC), and Machine-to-Machine (M2M) communication may be implemented by beamforming, MIMO, and array antennas. Application of a cloud Radio Access Network (RAN) as the above-described Big Data processing technology may also be considered to be as an example of convergence between the 5G technology and the IoT technology.
Device to Device (D2D) communication is being studied in communication standard groups to enable data communication services and proximity (or discovery) services between the UEs. Discovery is a process which determines that a D2D enabled User Equipment (UE) is in proximity of another D2D enabled UE. A discovering D2D enabled UE determines whether or not another D2D enabled UE is of interest to it using D2D Discovery. A D2D enabled UE is of interest to a discovering D2D enabled UE if its proximity is known by one or more authorized applications on the discovering D2D enabled UE. For e.g. a social networking application can be enabled to use D2D discovery feature. The D2D discovery is enabled on the D2D enabled UE of a given user for a social networking application to discovery and be discoverable by the D2D enabled UEs of his/her friends. In another example the D2D discovery is enabled on the D2D enabled UE of a given user for a search application to discover stores/restaurants etc. of its interest in its proximity. D2D enabled UE discovers other D2D enabled UEs in its proximity by using direct UE-to-UE signaling.
During the D2D communication a transmitting D2D UE transmits data packets to a group of D2D UEs or broadcast data packets to all the D2D UEs or sends unicast data packets to a specific D2D UE. D2D communication between the transmitter and receiver(s) is connectionless in nature i.e. there is no connection setup (or no control messages are exchanged) between the transmitter and receiver before the transmitter starts transmitting the data packets. During the transmission, the transmitter includes the source ID and the destination ID in the data packets. The source ID is set to the UE ID of the transmitter. The destination ID is the intended recipient of the transmitted packet. The destination ID indicates whether the packet is a broadcast packet or a unicast packet or a packet intended for a group.
During the discovery process the announcing UE (or discoverable UE) transmits a discovery message. The discovery message is transmitted by the D2D UE on discovery channel or discovery resources. The monitoring UE monitors the discovery resources to discover UE in its proximity.